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debugfs: make sure we can remove u32_array files cleanly

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debugfs_create_u32_array() allocates a small structure to wrap
the data and size information about the array. If users ever
try to remove the file this leads to a leak since nothing ever
frees this wrapper.

That said there are no upstream users of debugfs_create_u32_array()
that'd remove a u32 array file (we only have one u32 array user in
CMA), so there is no real bug here.

Make callers pass a wrapper they allocated. This way the lifetime
management of the wrapper is on the caller, and we can avoid the
potential leak in debugfs.

CC: Chucheng Luo <luochucheng@vivo.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jakub Kicinski 2020-07-09 17:42:44 -07:00 committed by David S. Miller
parent 8fb49c0109
commit a2b992c828
5 changed files with 31 additions and 30 deletions
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12
Documentation/filesystems/debugfs.rst
View File

@ -185,13 +185,17 @@ byte offsets over a base for the register block.
If you want to dump an u32 array in debugfs, you can create file with::
struct debugfs_u32_array {
u32 *array;
u32 n_elements;
};
void debugfs_create_u32_array(const char *name, umode_t mode,
struct dentry *parent,
u32 *array, u32 elements);
struct debugfs_u32_array *array);
The "array" argument provides data, and the "elements" argument is
the number of elements in the array. Note: Once array is created its
size can not be changed.
The "array" argument wraps a pointer to the array's data and the number
of its elements. Note: Once array is created its size can not be changed.
There is a helper function to create device related seq_file::

27
fs/debugfs/file.c
View File

@ -918,11 +918,6 @@ struct dentry *debugfs_create_blob(const char *name, umode_t mode,
}
EXPORT_SYMBOL_GPL(debugfs_create_blob);
struct array_data {
void *array;
u32 elements;
};
static size_t u32_format_array(char *buf, size_t bufsize,
u32 *array, int array_size)
{
@ -943,8 +938,8 @@ static size_t u32_format_array(char *buf, size_t bufsize,
static int u32_array_open(struct inode *inode, struct file *file)
{
struct array_data *data = inode->i_private;
int size, elements = data->elements;
struct debugfs_u32_array *data = inode->i_private;
int size, elements = data->n_elements;
char *buf;
/*
@ -959,7 +954,7 @@ static int u32_array_open(struct inode *inode, struct file *file)
buf[size] = 0;
file->private_data = buf;
u32_format_array(buf, size, data->array, data->elements);
u32_format_array(buf, size, data->array, data->n_elements);
return nonseekable_open(inode, file);
}
@ -996,8 +991,7 @@ static const struct file_operations u32_array_fops = {
* @parent: a pointer to the parent dentry for this file. This should be a
* directory dentry if set. If this parameter is %NULL, then the
* file will be created in the root of the debugfs filesystem.
* @array: u32 array that provides data.
* @elements: total number of elements in the array.
* @array: wrapper struct containing data pointer and size of the array.
*
* This function creates a file in debugfs with the given name that exports
* @array as data. If the @mode variable is so set it can be read from.
@ -1005,17 +999,10 @@ static const struct file_operations u32_array_fops = {
* Once array is created its size can not be changed.
*/
void debugfs_create_u32_array(const char *name, umode_t mode,
struct dentry *parent, u32 *array, u32 elements)
struct dentry *parent,
struct debugfs_u32_array *array)
{
struct array_data *data = kmalloc(sizeof(*data), GFP_KERNEL);
if (data == NULL)
return;
data->array = array;
data->elements = elements;
debugfs_create_file_unsafe(name, mode, parent, data, &u32_array_fops);
debugfs_create_file_unsafe(name, mode, parent, array, &u32_array_fops);
}
EXPORT_SYMBOL_GPL(debugfs_create_u32_array);

12
include/linux/debugfs.h
View File

@ -38,6 +38,11 @@ struct debugfs_regset32 {
struct device *dev; /* Optional device for Runtime PM */
};
struct debugfs_u32_array {
u32 *array;
u32 n_elements;
};
extern struct dentry *arch_debugfs_dir;
#define DEFINE_DEBUGFS_ATTRIBUTE(__fops, __get, __set, __fmt) \
@ -136,7 +141,8 @@ void debugfs_print_regs32(struct seq_file *s, const struct debugfs_reg32 *regs,
int nregs, void __iomem *base, char *prefix);
void debugfs_create_u32_array(const char *name, umode_t mode,
struct dentry *parent, u32 *array, u32 elements);
struct dentry *parent,
struct debugfs_u32_array *array);
struct dentry *debugfs_create_devm_seqfile(struct device *dev, const char *name,
struct dentry *parent,
@ -316,8 +322,8 @@ static inline bool debugfs_initialized(void)
}
static inline void debugfs_create_u32_array(const char *name, umode_t mode,
struct dentry *parent, u32 *array,
u32 elements)
struct dentry *parent,
struct debugfs_u32_array *array)
{
}

3
mm/cma.h
View File

@ -2,6 +2,8 @@
#ifndef __MM_CMA_H__
#define __MM_CMA_H__
#include <linux/debugfs.h>
struct cma {
unsigned long base_pfn;
unsigned long count;
@ -11,6 +13,7 @@ struct cma {
#ifdef CONFIG_CMA_DEBUGFS
struct hlist_head mem_head;
spinlock_t mem_head_lock;
struct debugfs_u32_array dfs_bitmap;
#endif
const char *name;
};

7
mm/cma_debug.c
View File

@ -164,7 +164,6 @@ static void cma_debugfs_add_one(struct cma *cma, struct dentry *root_dentry)
{
struct dentry *tmp;
char name[16];
int u32s;
scnprintf(name, sizeof(name), "cma-%s", cma->name);
@ -180,8 +179,10 @@ static void cma_debugfs_add_one(struct cma *cma, struct dentry *root_dentry)
debugfs_create_file("used", 0444, tmp, cma, &cma_used_fops);
debugfs_create_file("maxchunk", 0444, tmp, cma, &cma_maxchunk_fops);
u32s = DIV_ROUND_UP(cma_bitmap_maxno(cma), BITS_PER_BYTE * sizeof(u32));
debugfs_create_u32_array("bitmap", 0444, tmp, (u32 *)cma->bitmap, u32s);
cma->dfs_bitmap.array = (u32 *)cma->bitmap;
cma->dfs_bitmap.n_elements = DIV_ROUND_UP(cma_bitmap_maxno(cma),
BITS_PER_BYTE * sizeof(u32));
debugfs_create_u32_array("bitmap", 0444, tmp, &cma->dfs_bitmap);
}
static int __init cma_debugfs_init(void)